Apparatus for rolling disks



May 21, 1963 c. s. SHUMAKER APPARATUS FOR ROLLING DISKS Jmw mm NW 60 5 Sheets-Sheet 1 CHARLES s. SHUMA KER HIS ATTORNEY May 21, 1963 c. s. SHUMAKER APPARATUS FOR ROLLING msxs 5 Sheets-Sheet 2 Filed May 18, 1959 INVENTOR. CHARLES S. SHUMAKE R HIS ATTORNEY May 21, 1963 c. s. SHUMAKER APPARATUS FOR ROLLING DISKS 5 SheetsSheet 3 Filed May 18, 1959 CHARLES S. SHUMAKER yaw HIS ATTORNEY May 21, 1963 c. s. SHUMAKER APPARATUS FOR ROLLING DISKS 5 Sheets-Sheet 4 Filed May 18, 1959 INVENTOR.

R E u M U. H, Y E s N s R m m A; M F @f Y B May 21, 1963 c. s. SHUMAKER APPARATUS FOR ROLLING DISKS 5 Sheets-Sheet 5 Filed May 18, 1959 nmm QZM

HIS ATTORNEY United States Patent 3,090,265 APPARATUS FOR ROLLING DISKS Charles S. Shumaker, Glenshaw, Pa., assignor, by mesne assignments, to Kelsey-Hayes Company, Detroit, Mich, a corporation of Delaware Filed May 18, 1959, Ser. No. 813,812 2 Claims. (Cl. 80-16) This invention relates to an apparatus for cold forming principally by rolling of disks having a variable thickness contour such as are commonly used in the manufacture of heavy duty vehicle wheels, harrow disks, and turbine and compressor rotor disks and the like.

A measure of success has been realized in the industry with respect to the production of disks having a given contour, attained by heating the blanks to a sufliciently high temperature to permit them to be readily rolled into the shape desired. Disks produced by hot rolling, however, do not possess metallurgical properties necessary to meet critical requirements as are presently demanded. A number of methods and apparatuses, also, have been developed in recent years for the cold rolling or spinning of contoured disks, but none of them have been consistently able to produce disks which are wholly acceptable in all events with respect to smoothness of finish or adaptability of being drawn directly.

One of the objects of the present invention is to provide an apparatus for forming contoured disks in a highly efficient and economical manner.

Another object of this invention is to provide for simultaneously forming a pair of variable thickness disks from a pair of constant thickness circular blanks by employing two pairs of cooperating reducing rolls, the reducing action of which is so controlled that disks of accurate predetermined desired contours are assured.

A further object of this invention is to provide an apparatus for forming disks in which two pairs of opposed cooperating rolls having a given contour are diametrically arranged and brought into a rolling relationship with a pair of blank disks positioned in a back to back relationship, the pairs of rolls being movable simultaneously in an axial outward direction.

It is a further object of this invention to provide an apparatus simultaneously forming contoured disks from a pair of blanks of uniform thickness in which the blanks are reduced from their inner areas outward by rolls having predetermined contoured portions, the leading portion of each roll being arranged to immediately precede the portion of the roll employed for reducing by rolling and adapted to restrain the unrolled metal thereby to cause a reduction by elongation prior to being engaged by the reducing portions of the rolls.

It is another object of this invention to provide an apparatus forming contoured disks in which a pair of superposed disk blanks are simultaneously reduced to a predetermined controlled contour by engaging the inner areas of the disks simultaneously and performing a rolling operation thereon by pairs of cooperating contour shaping and reducing rolls and engaging the outer peripheral areas of the disks immediately ahead of the reduced rolled areas to restrain the outer peripheral areas in a manner to cause the outer peripheral areas to be reduced by elongation prior to being engaged by the reducing rolling portions of the rolls, and engaging the areas of the disks subsequent to rolling to burnish the area thus rolled.

It is a still further object of this invention to provide an apparatus for producing uniformly tapered disks from blanks of uniform thickness positioned in back to back relationship in which two pairs of rolls are employed, one pair of which is inverted with respect to the other and each pair including a forming roll and an anvil roll.

It is another object of this invention to provide a roll adapted to produce a disk of a given contour from a disk having a substantially uniform thickness including a rolling portion for reducing the disk, a burnishing portion adapted to burnish the rolled portion of the disk and a confining portion adapted to confine and to reduce a portion of the disk in advance of the portion reduced by rolling.

It is a still further object of this invention to provide a cooperating pair of tapered disk rolling rolls in which one roll is an anvil roll and the other roll is a forming roll.

These objects as well as the various other novel features and advantages of this invention will become apparent from the following description and accompanying drawings of which: 7 FIG. 1 is a plan view of a disk forming mill in which the novel rolls as disclosed herein are incorporated and the operation of the method of producing disks as defined herein may be practiced;

FIG. 2 is a front elevational view of the disk forming mill shown in FIG. 1;

FIG. 3 is a partial sectional elevational side view taken at lines III-III of FIG. 1;

FIG. 4 is a sectional elevational end view taken at lines IV-IV of FIG. 3;

FIG. 5 is an enlarged view of a portion of one pair of reducing rolls shown in FIG. 2 in which three positions taken by the rolls are indicated as a pair of blanks is traversed during a disk forming operation;

FIG. 6 is an enlarged view of portions of two pairs of modified disk forming rolls showing the rolls in engagement with a pair of blanks during a forming operation, and

FIG. 7 is an enlarged view of a portion of one pair of rolls further modified to incorporate some of the features of the rolls shown in both FIGS. 5 and 6.

With reference to FIGS. 1 and 2, there is illustrated therein a mill for forming disks which embodies the features of the invention herein disclosed incorporating a rigidly constructed unitary housing 11 having 'T-shaped post sections 12 formed on the outside surfaces of two of the opposite sides thereof. The lower ends of two sides of the housing terminate into pairs of spaced apart outwardly extending shoes 13 which rest upon individual parallel disposed bedplates M, the bedplates being of sufficient length to extend beyond the ends of the housing and being supported on suitable foundations provided for the purpose. Windows 15 are formed in the housing and centrally located in the opposite two sides thereof which are surrounded by the T-shaped sections 12. In addition, windows 16 are also provided in the remaining opposite sides of the housing so that the configuration of the housing constitutes four vertical rigid posts joined together by thick top and bottom sections to form an integral unit.

With reference now to FlGS. 3 and 4, it will be appreciatedthat the elements illustrated therein having identifying numerals including the lower case letter b are identical to and symmetrically arranged with respect to other elements contained in the left hand portion of the mill.

as shown in FIGS. 1 and 2. Where the elements of the left hand portion of the mill are identified, lower case letter a is included with the numerals.

In the upper and lower extremities of the housing 11 extending horizontally through the windows 15, lower and upper channel shaped cross-heads 17 and 18 are provided, the upper cross-head 18, when assembled in the housing, being arranged in an inverted position with respect to cross-head 17, as best shown in FIG. 4.

The four inside flat surfaces of the web portions of the channel shaped cross-heads 17 and 18 that extend within the windows are provided with a raised central portion having centrally located grooves or guides 22 into which there are received complementary projecting portions of two pairs of corresponding wedges 23b and 24b. These wedges are supported along their entire length within the housing and the width thereof corresponds to the width of the raised central portions of the cross-heads and are so arranged that the narrow ends thereof will extend towards the vertical centerline of the mill. The lower wedge element 231), as shown in FIG. 4, is prevented from moving longitudinally by key 25 which is positioned in transversely arranged keyways provided in both the wedge and the lower cross-head. The upper wedge 24b, in contrast to the wedge 23b, is permitted to move in a horizontal direction in the guides 22 within the cross-head. This horizontal movement is accomplished by an individual high pressure piston cylinder assembly 26b connected to the outboard end of the wedge and secured to and supported by a sliding casting 27b. Each of the wedges 23b and 24b has a centrally located groove 28 provided on the inclined surface thereof into which there is received a complementary projection provided on the inclined surfaces of other wedges 31b and 321) respectively which, though of the same width as the wedges 23b and 2412, are somewhat greater in length. The ends of the wedges 31b and 32b which extend away from the mill are connected to individual high pressure piston cylinder assemblies 33!) and 3412 respectively by which the wedgesare moved horizontally to effect vertical displacement of the rolls. The piston cylinder assemblies-33b and 3417, as shown in FIG. 3, are mounted on suitable trunnions on extended portions of the cross-heads so asto permit the piston cylinder assemblies to pivot during operation.

Engaged with the horizontal flat surfaces of wedges 31b and 3215 there are two cam holders 35b and 36b, the lower holders 35b, as best shown in FIG. 4, being inverted with respect to holder 36b. The holders are restrained from moving transversely and longitudinally by suitable vertical guide surfaces provided on the crossheads. By this construction, the cam holders are permitted to move vertically only. Into the open sides of the holders 35b and 36b, wedge shaped cams 37b and 38b respectively are received, these cams being shonter in length than the opening in the holders in order to facilitate ease of assembly.

Extending between the pairs of cams 37b and 38b and arranged in the same vertical plane, also as shown in FIG. 3, there are located in each window 15 one pair of individual chock assemblies 3% and 41!), the checks being arranged on opposite sides of the horizontal centerline of the mill. The checks are made in the form of hollow tubular castings, the inboard ends being in the form of heavy rectangular sections having straight vertical sides corresponding to the sides of the housing post as best seen in FIG. 4.

Each of the chocks incorporates spaced apart roller bearings 42 and 43 which rotatably support longitudinally extending shafts 44b and 45b. The bearings 42 are of heavy duty type, as indicated in FIG. 3, in order to support adequately the overhanging load imposed during rolling upon .the inboard ends of the shafts. In the vertical plane containing the large bearings 42 and on the sides of the chocks farthest away from the horizontal centerline of the mill, the chocks are vertically extended and in the extended portions thereof annular recesses are provided for receiving bearings 46 which rotatably support the journals of cam rollers or followers 47b and 48b. The axes of the cam rollers 47b and 48b are arranged at right angles to the axes of the shafts 44b and 45b. The bearings 46 are maintained in their proper location by bearing caps 49 which are attached to the chocks by bolts or other suitable fastening means. ,It is apparent, from FIG. 3, that the cam rollers 47!) and 48b are adapted to rest on and travel over the cams 37b and 38b, the cams being made sufliciently long to provide sutficient backing-up support for the cam rollers during a disk forming operation.

At the outboard ends of each chock 39b and 41b there are two extensions 51b and the extensions of the two checks 3% and 411) are pivotally connected together by a pin 52?) secured to spindle support stand 53b arranged at the ends of the shafts 44b and 45b. The axis of the pivot establishes the horizontal pass line or centerline of the mill. This pivotal arrangement permits the chocks to be moved toward and away from each other. A pair of piston cylinder assemblies 54b is arranged at the roll end of the lower chock assembly 3%, as best shown in FIG. 4, with the ends of the pistons thereof engaged with the lower surfaces of the upper chock assembly 41b and by which means the top checks are supported and the cam rollers 47b and 48b held against the cams 37b and 381) respectively. The spindle stand 53b is arranged between the outer ends of the shafts 44b and 45b and the motor 551), as best shown in FIGS. 1 and 2, the stands supporting the pivoted outboard ends of chocks 39b and 41b. The outer ends of the shafts 44b and 45b are connected by suitable spindles 56b and 57b to the output side of a common gear drive 5811. To the input shaft of the gear drive there is connected a motor 5517.

To the enlarged inboard ends of shafts 44b and 45b, which extend beyond the ends of the shocks 3% and 41b, as shown in FIG. 3, there are affixed by means of suitable countersunk bolts 59 two cooperating large diameter relatively narrow width contour forming rolls 61b and 62b. The contours of the rolls are so defined as to serve certain functions during a disk forming operation including rolling, confining or restraining and burnishing, the details concerning which will be more fully discussed hereinafter.

Similar platforms 63a and 63b are provided on each side of the mill, as shown in FIGS. 1 and 2, and to which there are secured respectively spindle stands 53a and 53b, gear drives 58a and 58b and motors 55a and 55b. The platforms 63a and 63b are mounted for longitudinal slidable movement upon suitable guides 64a and 64b respectively as shown in 'FIG. 1, alfixed to sub-platforms 65a and 65b. To the sub-platform 65a there is attached a double acting extended long stroke piston cylinder assembly 66, the piston rod 67 of which extends in a direction away from the mill and secured by a bracket 68 to the outer end of the platform 63a. Beneath the platform 63a and secured to a bracket 69 which extends downward from platform 6311, there is attached an equalizer tension rod 71 which passes beneath the mill in a direction toward the other platform 65b. Secured to the other end of the rod 71 there is a rack 72, see FIG. 2, the teeth of which are formed on the upper sides thereof. Rotatably secured to the lower portion of the sub-platform 65b, there is a roller 73 which acts to guide and support the rack 72 as it is moved longitudinally. Engaged with the teeth of the rack 72 there is a large pinion 74 which is also rotatably secured to the sub-platform 65b. Beneath the platform 63b there is also a rack 75, the teeth of which are on the lower side thereof and in mesh with the teeth of the pinion 74. Thus, by this equalizing arrangement, when the platform 63a is moved outward to the left on actuation of the piston rod 67, the platform 63b will also be moved outward for the same distance but in a direction to the right.

With reference to FIGS. 3 and 6, there is shown therein the spindle assembly 76 provided for supporting the disks prior to and after reduction of the blanks and also a holddown assembly 77 for engaging the disks from above during the reducing operation. The holddown assembly is connected to and raised and lowered by a piston cylinder assembly 78 located at the upper portion of the mill.

Suitable loading and unloading devices 79 and 81 respectively are shown with the mill in FIG. 1. The loading device 79 is so devised as to receive a pair of blank disks and place them upon the spindle assembly 76 for carrying out a reducing operation and the unloader 81 is operable to engage with the same pair of disks following a reducing operation for removing the finished product from the mill.

-It will be apparent from the aforesaid description of the major component elements of the mill that the mill rolls 61b and 62b will be brought into and out of the rolling position by operation of the cylinders 33b and 34b to thereby move the Wedges 31b and 32b. The desired initial roll opening is obtained by operating the cylinder 26b to move the wedge 24b to a position corresponding to the desired initial roll opening. Once this is eifected, the rolls 61b and 62b as they are traversed will be displaced by the cam rollers 47b and 48b passing over the cams 37b and 38b.

With reference to FIG. 3, it will be observed that the reducing rolls, of which but the right hand pair 61b and 62b is shown, are of such dimensions that they are relatively narrow in comparison with the diameters thereof. The roll contour is considered to be of utmost importance for successful high production operation of the mill. It is not merely sufiicient to provide rolls which reduce the blanks to obtain the proper contour or taper desired, but the rolls must be of such a shape as to permit rapid withdrawal generally in radial direction across the disks for purposes of high production, but the rolls must also be capable of producing a smooth rolled surface while at the same time avoiding excessive workhardening and splitting of the peripheral edges of the rolled disks.

The particular contours of the rolls employed in FIG. 3 are shown in greater detail in the sequence diagram FIG. 5 which illustrates three of the positions taken by the rolls as a pair of blanks is traversed radially during a disk forming operation. Three particular positions of the rolls during a rolling sequence are indicated at R R R R and R R and the rolls in these respective positions are shown by dotted lines, full lines and dot and dash lines respectively. With reference to position R 11 the rolls are divided into a burnishing portion ab, reducing roll-ing portion b-c, relieved portion cd and lead-in portion d-ef. The portion ab is formed on the same or a slightly greater angle than that of the taper to be formed on the disks. Of course, as rolling commences the angle to be employed for the burnishing portion of the rolls will depend considerably upon the characteristics of the mill such as the deflection of roll shafts, angular opening and closing of the rolls, in order to assure the operator that the burnishing portion of the roll will remain at the proper angle during the reducing operation. The reducing portion of the rolls bc provides for carrying out the actual reduction by rolling of the disks being formed. Adjacent to this portion there is a relieved area c-d which serves to concentrate the rolling action to the portion b-c. The lead-in portion d-e-f is divided into two sub-portions d-e being the part which serves to confine the edges of the disks in order to attain one of the advantages of this invention and ef a portion which prevents undue curling of the disks. The edge portions of the disks as indicated within the area de have already been somewhat reduced but not by actual rolling since that portion of the disks has not as yet been contacted by the rolling portion bc of the rolls. If it were not for the restraining or confining action of the roll portions d-e, the edges of the disks would curl so that the disks at that point would be ruffled or dish shaped. However, the portion d-e, serving to prevent curling. actually causes the radial compressive forces incident to the rolling action to so act upon the disks that the portions of the disks within the de portion of the rolls is reduced by elongation. The disks are further reduced by withdrawing the rolls radially from the position R R to the position R R at which point the rolls are opened up and withdrawn beyond the edges of the disks for permitting ready removal of the finished tapered disks from the mill. It is to be noted that this invention provides for reducing disks to the proper dimensions without actually roll-ing the disks to the very edge. The unrolled edge portions of the disks will be trimmed off prior to being processed in subsequent operations.

The degree of taper, the angle of the restraining portion and the length of the lead-in portion of the rolls will depend upon the dimension of the blanks inasmuch as the taper is influenced by the bite angle of the rolls which angle is to be maintained small in order to permit a rapid withdrawal of the rolls to complete a reducing operation. The angle of the restraining surface is influenced by the thickness of the blanks and the length of the restraining surface is influenced by both the thickness of the blanks and by the original and finished diameters of the disks.

By reason of the fact that there is an actual reduction of a portion of the metal prior to actual contact with the rolling reducing portions of the rolls, the entry of the metal into the bite of the rolls will be quite gradual resulting in a smooth gentle rolling action which .would not be the case if the disks were not restrained and were permitted to curl to their fullest extent during rolling. Since this relationship is maintained throughout the rolling cycle, as the blanks are progressively reduced in thickness by an actual rolling action, there is a corresponding progressive reduction in thickness of the metal outboard of the area being rolled which, as explained heretofore, results from elongation due to the restraining action of the rolls. Where the edges of the disks are rolled as in present day practice, hardness has been found to be as high as 110 Rockwell B whereas the hardness of disks produced by the method disclosed herein has been found to be of the order of Rockwell B. With respect to the burnishing action, this, of course, takes place immediately after reduction by rolling, the burnishing portion of the roll serving not only to burnish but to act as a support for the rolls so as to prevent the reducing portion of the roll from actually pinching the disks at the edge which obviously would result in nonacceptable disks.

A modified form of reducing rolls which may be employed in the mill is as shown in FIG. 6 of which there are two pairs of rolls, each pair consisting of a reducing ro1l82a and 82b and anvil rolls 83a and 83b. As will be noted, the two pairs of rolls are inverted relative to each other so that reduction of the upper disk can be independently controlled by the left hand pair of rolls 82a and 83a and reduction of the lower disk by the right hand pair of rolls 82b and 83b. The reducing rolls 82a and 82b make contact with the disks for a distance designated between the points XY Whereas the anvil rolls make contact with the disks for a greater distance as designated by the points XZ. By this arrangement, it is possible to control the rolling operation so that the disks after being reduced are of the same cross-section, that is, with neither of the disks being over rolled with respect to the other. Should it be found that the rolls as shown in FIG. 6' are not properly adjusted so that the upper disk, for example, tends to be reduced more than the lower disk, as would be indicated were the top disk to attain a larger diameter during forming than the lower disk, the operator need merely to adjust the left hand set of rolls to provide the necessary increased roll opening for the rolls 82a and 83a. This increased opening will decrease the unit rolling pressure applied to the upper reducing roll 82a so that there will be a decreased reduction of the upper disk. This adjustment is made to balance the reduction of the two disks and the finished diameters will be the same. While there is shown in FIG. 6 to be a marked contrast bet-ween the contours of the rolls designated 82a and 82b and those designated as anvil r-olls 83a and 83b respectively, it has been found that such a great difference between the reducing and anvil rolls is not necessary for practicing the invention herein disclosed. It is sufficient that the area of contact of the anvil rolls be but slightly greater than the area of contact of the reducing rolls so that the roll having the greater area of contact will always serve as a positive anvil and the roll of lesser area as the reducing roll.

With reference to FIG. 5, showing three positions of two pairs of similar rolls 61b and 6%, the rolls during a reducing operation contact the disks at the first reducing position R R the portion of the roll a-b not as yet making contact. As the rolls are withdrawn outward, one of the positions attained is that indicated at R R shown in full lines. During the time the rolls move from position R R to position R R a portion of the disks has already been reduced without actually being rolled as is apparent when the disk portions indicated in dotted lines are compared with the corresponding disk portions as indicated in full lines. Up to position R R three operations have actually been performed upon the disks namely; reduction due to rolling by the roll portion bc, reduction due to elongation caused by the restraining or confining action at the edges of the disks between the roll portions c-d and burnishing of the rolled disk by the roll portion indicated at ab.

After the rolls have reached their positions on the disks as shown in dot and dash lines, the reducing operation is then completed. The next immediate step is to open the reducing rolls so that on further withdrawal of the rolls outward of the disks the rolls will not contact the extreme edges thereby preventing workhardening of the disk edge portions.

With respect to the modified form of reducing rolls as shown in FIG. 6, reduction by rolling takes place on the diagonally opposite side inasmuch as each pair of rolls comprises a reducing roll 82a and a diagonally opposite reducing roll 82b and an anvil roll 83a and a diagonally opposite anvil roll 83b respectively. Reduction of the disks by these rolls is very readily controlled for if it should be found that the disks do not have the same thickness at corresponding points radially outward of their centers merely by adjusting the pair of rolls which produces the off-dimension disk, the taper of both disks will be made uniform by reason of the controlled balanced condition thus etfected during the reducing operation. Thus by employing rolls having the characteristics as outlined and due to the controlled conditions obtainable, blanks of a minimum diameter may be used to obtain the required size of finished disk which would not otherwise be the case if over rolling of one disk relative to the other should normally take place. If one disk should over roll the other, it is obvious that larger blanks would have to be supplied in order that the diameter of the finished disks will be at least of the diameter required. Where this precaution must be taken, a considerable waste of metal is the result.

With reference to drawing FIG. 7, there, is illustrated therein one pair of two pairs of reducing rolls which have been further modified to incorporate some of the features of the rolls shown in bothjFIGS. 5 and 6. Both rolls 84b and 85b include a lead-in portion de'--f similar to the lead-in portion def of rolls 61b and 62b illustrated in FIG. 5. However, roll 84b is provided with a rather short portion a-b' thereby constituting the roll 8412 the reducing roll Whereas roll 85b is provided with a rather long portion 'a"-b thereby constituting that roll the anvil or supporting roll. Although the other pair of rolls is not shown, it is to be understood that that pair is inverted with respect to the position of the rolls 84b and b. As in the case of the rolls of FIG. 6,

- similar to that for the rolls 82a, 83a, 82b and 83b shown in FIG. 6. However, when the disks are restrained and prevented from curling in the confining lead-in portion from c outward, the unrolled portion of the disks will be elongated in a fashion similar to that which takes place with respect to the rolls 61b and 62b shown in FIG. 5. Thus, by this modification, controlled rolling obtainable by employing reducing and anvil rolls is supplemented by the additional advantage of avoiding over rolling of the disk area adjacent to the edges. Although the drawings for purposes of illustration show a pair of blanks as being simultaneously processed in the mill disclosed herein, it is to be appreciated that the apparatus may be employed for processing one or more disks at the same time.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated and described what I consider to represent the best embodiment thereof. However, I desire to have it understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In a mill for simultaneously forming a pair of disks from blanks of a substantially uniform thickness, two pairs of rolls each pair comprising one roll having an extended relatively constant diameter portion for contacting and supporting a substantial portion of a blank from one side and the other having a relatively narrow portion for engaging and reducing said blank from the side opposite said first roll, said pairs of rolls spaced diametrically apart with respect to the centers of said blanks and one pair inverted with respect to the other.

2. In a mill for simultaneously forming a pair of disks from blanks of a substantially uniform thickness, two pairs of rolls each pair comprising one roll having a relatively wide portion for at least engaging a substantial portion of a blank from one side and the other having a relatively narrow portion for engaging and reducing said blank from the side opposite said first roll, said pairs of rolls spaced diametrically apart with respect to the centers of said blanks and one pair inverted with respect to the other.

References Cited in the file of this patent UNITED STATES PATENTS 1,208,831 Putnam Dec. 19, 1916 1,534,860 Martin Mar. 21, 1925 1,795,492 Kelley Mar. 10, 1931 1,911,460 Moody May 30, 1933 1,923,389 Otte Aug. 22, 1933 2,020,652 Lennox Nov. 12, 1935 2,342,159 Moran Feb. 22, 1944 2,588,651 Nelson Mar. 11, 1952 2,911,864 Nelson Nov. 10, 1959 2,942,504 Sharpe June 28, 1960 FOREIGN PATENTS 837,687 Germany May 2, 1952 

2. IN A MILL FOR SIMULTANEOUSLY FORMING A PAIR OF DISKS FROM BLANKS OF A SUBSTANTIALLY UNIFORM THICKNESS, TWO PAIRS OF ROLLS EACH PAIR COMPRISING ONE ROLL HAVING A RELATIVELY WIDE PORTION FOR AT LEAST ENGAGING A SUBSTANTIAL PORTION OF A BLANK FROM ONE SIDE AND THE OTHER HAVING A RELATIVELY NARROW PORTION FOR ENGAGING AND REDUCING SAID BLANK FROM THE SIDE OPPOSITE SAID FIRST ROLL, SAID PAIRS OF ROLLS SPACED DIAMETRICALLY APART WITH RESPECT TO THE CENTERS OF SAID BLANKS AND ONE PAIR INVERTED WITH RESPECT TO THE OTHER. 